Project Summary/Abstract Core B Photodynamic therapy (PDT) is activated by light, and the tumors that are treated by PDT are accessible to light either directly or via optical fibers advanced through needles or catheters. Thus optics plays a central role in planning and administering PDT and in monitoring response to therapy. The Optics Core of this program project supports the optics and physics needs of all of the projects with particular emphasis on facilitating the definitive clinical trials in head and neck cancer. Toward these ends, we have proposed the following three specific aims: (1) To acquire, characterize, disseminate, and support the commercial Zenascope spectroscopy system for the multi-center trials of HPPH-PDT in (i) T1/T2 N0 tumors of the oral cavity and oropharynx (Project I, Specific Aim 1) and (ii) patients with locally advanced recurrent HNSCC who have failed radiation (Project 1, Specific Aim 2). In the first of these trials, spectroscopy will be used to evaluate possible predictors of treatment response. In the second trial, optical properties derived from reflectance measurements will be incorporated into PDT treatment plans. Reflectance spectroscopy was used successfully at RPCI in the oral cavity PDT clinical trial of the previous funding period. Zenascope reflectance spectroscopy systems will be placed at the four participating clinical trial sites. The Core will support these systems, train users at Rochester, Johns Hopkins, Minnesota, and RPCI, and be responsible for data analysis and interpretation; (2) To provide and further optimize image-based interstitial PDT treatment planning for a multi-center Phase II trial of HPPH-PDT in patients with locally advanced recurrent HNSCC who have failed radiation (Project 1, Specific Aim 2). Target volumes and surrounding normal structures defined on patient CT scans will be incorporated into treatment planning simulation codes. Informed by pre-treatment measurements of tumor optical properties, an initial treatment plan will be created. The plan will be evaluated based on interstitial fluence measurements using a dosimetry system developed at RPCI; and (3) To provide routine engineering and optics support for the clinical and preclinical research efforts of the program project. These responsibilities include technical support for the clinical and preclinical lasers at RPCI and the fabrication and maintenance of fiber delivery systems.